


(p)reset

by kokofas



Series: revelations [1]
Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Alpha Ishigami Senkuu, Alpha/Beta/Omega Dynamics, Both Senku and Gen are consenting adults, Canon Compliant, Canon Universe, Characters are their ages from the manga, Discussion of mpreg, Eventual Happy Ending, Intersex Omegas, Knotting, M/M, Mating Cycles/In Heat, Mpreg, Omega Asagiri Gen, Omegaverse, Oral Sex, Picks up at the last episode of Dr. Stone S1, Scenting
Language: English
Status: In-Progress
Published: 2021-01-18
Updated: 2021-02-02
Packaged: 2021-03-16 17:02:27
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 9,422
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28834578
Author URL: https://archiveofourown.org/users/kokofas/pseuds/kokofas
Summary: Aside from the scars left behind on those who'd de-petrified, Senku assumed that no other phenotypic changes had happened as a result of the petrification wave. Now, with the Spring fast approaching, he’s starting to notice peculiar changes in Gen. Ever the curious mind, he begins to puzzle over what could be happening with the other man, particularly with that strange scent that seems to follow him around. If only Gen would stop avoiding him, and if only they weren’t busy with the work needed to defeat the Tsukasa Empire.NOTE: Senku and Gen are 19 and 21 respectively in this fic, like their current ages in the manga.
Relationships: Asagiri Gen/Ishigami Senkuu
Series: revelations [1]
Series URL: https://archiveofourown.org/series/2114205
Comments: 24
Kudos: 168





	1. Chapter 1

**Author's Note:**

> Quick note: Male omegas in this fic have both reproductive organs (essentially intersex). Basically, the men who had become omegas due to the petrification wave woke up with new organs that they didn't have before (unless they were already intersex). I know this isn't a common hc in A/B/O, but I hope you'll enjoy it anyway!

Growing up, Senku had always had an attraction to the curious and the unknown. An inexplicable pull to take things apart, examine them, make sense of them, and shape them into something new. This attraction had been a blessing in some sense, and a curse in some. For instance, Senku knew that his mind was sharp, calculated, and quick. There were very few things that gave him pause, and he had never accepted the concept of impossibility. On the other hand, though, when Senku _did_ get interested in something exhilaratingly mysterious, there was no hope in coaxing him out of that interest, not until the puzzle that it presented was solved.

And this was why, while working on constructing the second cell phone necessary for winning their coming battle against Tsukasa’s empire, Senku felt irritated with himself. He had been noticing something peculiar the past few days. Or rather, something peculiar kept drawing his attention away from any task at hand, against his conscious will. Again and again, he was finding himself studying Gen, analysing his every utterance and footfall, trying to figure out exactly _what_ was causing his instincts to pay such a great deal of attention.

It really was the most painful type of exhilaration, when his scientific instincts were noticing something that his brain had yet to zero in on. When he still didn’t know what he was looking for, he had to restrain his instincts and keep them to himself, lest others thought he’s finally crossed the bridge to insanity.

And so this way of living continued, where Senku’s attention was divided at the best of times. After feeling disastrously distracted during their chemistry team-up, Senku had agreed with Kaseki -behind Gen’s back- to keep the man on his crafting team. So when Kaseki dragged Gen away to work with him, Senku allowed himself to breathe a sigh of relief.

The small separation he put between himself and Gen helped a little at first. With the other man out of sight, Senku was able to direct his attention to the multitudes of projects and calculations he needed to do. When a prickle of wonder came to him from the back of his mind, prodding him about Gen, he pushed it away without hesitation.

Still, when everyone joined back up to enjoy each other’s company and eat every night, he couldn’t help but notice the specific scent that Gen always carried around with him. He had assumed the man had figured out a way to distill essential oils from some natural scents, but after witnessing Gen’s _modest_ chemistry skills, he knew that couldn’t have been the case. So he found himself sideling up next to Gen, the other man perking up and offering him a kind face in greeting.

“So tell me,” He started, “If you’re so miserable at chemistry, how come you’re always wearing your signature scents?” He asked, genuinely curious but with a teasing tone.

Gen laughed, a nervousness barely making itself known under his words. “I’m not _that_ miserable at it.” He pushed Senku’s shoulder lightly. “Besides, what kind of mentalist would I be if I revealed my secrets?” He smirked, watching Senku’s face intently.

“Oh please, I don’t have time for those oldschool mental games right now.” Senku laughed and shook his head, causing the strands of hair framing his face to wave about with him.

“And which games would those be?” Gen asked, a hand reaching forward to teasingly tug on one of Senku’s strands before retreating back to holding onto his empty bowl.

“Hiding something incredibly simple behind a false mask of mystery and mastery.” Senku responded, refusing to fall for the distraction Gen introduced with his hand and keeping his eyes trained on Gen’s face.

“Senku!” Gen started, “You just read my job description to me.” He laughed, pushing Senku’s shoulder playfully again before rising to get another serving of beef ramen. Senku stayed seated, quiet and calculating, before Chrome settled down next to him and began talking loudly, drawing him out of his pondering thoughts.

* * *

Whatever essential oil technique Gen’s helper was using, (because Senku was certain Gen couldn’t distill an oil from a natural source to save his life), Senku had to admit that it was improving with each passing day. Gen’s usual mixture of scents, which Senku has dissected and identified as lavender, orange, pine, and black pepper, was becoming increasingly more prominent, and lingered in rooms long after he was gone. On days with harsh winds, the wind would carry Gen’s scent to Senku as if taunting him. He was losing his mind trying to figure out what Gen was doing to achieve this scent, to the point that he found himself glancing at the other man every few minutes, hoping to catch him in the act of reapplying the essential oils he had mysteriously managed to obtain.

This preoccupation was wearing on Senku’s patience- he was accustomed to conquering the things that piqued his curiosity quickly and easily so he could move on to the next thing. So when he found himself alone in the lab with Chrome, he figured he would ask.

“Chrome, can I ask you a question?” Senku started, not removing his eyes from the delicate titration he was in the midst of.

“ _You_ want to ask _me_ a question? Uh, sure.” Chrome frowned, confused by the change. When they were in the lab, it was often him asking Senku all the questions.

“It’s not about this. I was wondering if you were helping Gen with making essential oils?” He rose back up as he finished up with the titration, confident that he’d placed as close to the exact amount he needed in the beaker as humanly possible.

“Essential oils?” Chrome repeated, shaking his head. “It couldn’t have been me, I’ve never made essential oils. Why are you asking?”

“Because he won’t tell me who his supplier is.” Senku groaned, laughing at himself alongside Chrome.

“Why is he playing mentalist games with something like perfume?” Chrome laughed. “It’s probably him making it at night while we sleep.”

“No way, he couldn’t have. He’s dreadful at chemistry.” Senku gave Chrome a serious look, the expression alone convincing Chrome.

“That bad, huh.” Chrome laughed as Senku nodded solemnly. “Maybe he’s been visiting the herbalist in the village, you could pay her a visit and ask.” He suggested, patting Senku’s back compassionately. “I know you hate a mystery you can’t solve.”

Senku smirked. “There is no mystery that I can’t solve, Chrome. Remember?”

* * *

Well, visiting the herbalist was a bust. First, she assured Senku that Gen had never set foot in her shop. Second, it was clear to Senku that she has never extracted essential oils either, as she relied on drying and powdering natural items to extract their scent. When Senku examined her products, he knew that they weren’t what Gen was using, they were much more muted. While examining the lavender powder she had packed into little coconut shell containers, she insisted that he take some home, no trade needed, as a gift since he was village chief. As he walked back with the smell of lavender wafting from the coconut shell container, he thought it ironic that Gen’s scent seemed to latch onto him even when Gen wasn’t around to blame.

He placed the powdered scent on the desk he’d fashioned for himself from wood in his ‘bedroom’ (really the storeroom by day), deciding that he would gift it to Gen later since the man seemed so fond of lavender. 

From outside, Chrome’s and Kohaku’s voices carried to him, calling his name. He leaned out of his bedroom window, looking down at where they were standing.

“Senku! Come on, the village is about to do the annual winter swim!” Chrome beckoned him over with his hands.

“You’re village chief now, you’re supposed to be the one to start the event!” Kohaku helpfully supplied just as Senku was about to ask why he should care for something like that.

“Swimming on a February night? Are they trying to get sick?” Senku asked loudly, frowning at the irresponsibility of such an event. If anyone got sick, it would mean more labor going into producing a course of antibiotics.

“Just come down!” Kohaku called impatiently, causing him to sigh and rush back downstairs to the open. He slid his feet into his shoes, rimmed with fur for the cold months. Stepping out onto the snow with the two of them, he felt the baby hairs on his neck stand up in the cold, still air of a winter night.

“Where is it supposed to be?” He asked with just a hint of annoyance in his voice, following them as they guided him toward the main event. Apparently, everyone had already gathered up except him, though he swore nobody even told him it was happening.

“I definitely told you a week ago.” Chrome said, making Senku question himself. Just how much has he been distracted, that he forgot such a recent detail? He wasn’t used to being forgetful.

Nearer to the shore, where the swimming event was to be held, there was a steady frosty wind blowing that somehow managed to rattle Senku’s bones with each gust. He tightened his tunic, protecting his chest so as to not contract pneumonia or anything worse. It would be a disaster if he were to get sick right when Tsukasa means to attack. Cheers erupted as the three of them reached the rest of the group, people clearing a spot near the bonfire for them to occupy.

“Okay, so I don’t know what this is supposed to be. Anyone care to explain?” Senku asked, smiling as Suika jumped up to volunteer the information.

“Basically, adults from the village will swim from here to the other shore and back on this night every year as a way of asking for a blessed and plentiful spring!” Suika exclaimed, pointing from the shore they stood on to a nearby shore, perhaps 50 yards away. So that was 100 yards of pure torture, Senku thought grimly but did not say. 

“Let me guess, the person who finishes first will be the most blessed?” He guessed, smiling in amusement as the rest nodded. He was sure that this was some macho competition that the founders did to liven up the harsh winter, giving it this bizarre explanation to tease their children. He laughed imagining his father concocting this superstition behind it, wondering if he had done it just to mess with Senku. “Okay, well, what’s everyone waiting for?” He grinned, watching as people around him discarded their clothes to prepare to jump in.

“One last thing,” Suika said while tugging on his animal skin tunic, drawing his attention back to her. “As chief, you have to be the first to jump in!” She excitedly announced as he groaned.

“No way.” He shook his head as the others coaxed him by pushing him towards the edge of the water. He tried escaping their hold only to be pulled back by Magma, a grip he knew he wouldn’t be escaping anytime soon. He searched around until he found Gen who looked all too amused from where he stood near the bonfire. “Gen, you’ve got to convince them that lab nerds can’t swim that well!”

Gen snickered, brushing the longer side of his hair back without a care. “I think it may cause you less suffering to go along with them, Senku. But if you do drown, I promise to mourn your loss.” He pouted at the final note, laughing as Senku called him a traitor and gave up trying to escape the activity.

“Well, if I have to do this challenge, then so does Gen.” Senku changed strategies as he loosened the strings holding his tunic together, the top part of the fabric sliding down to his waist. Although his attention had been on Gen, he noticed that it was Kohaku’s eyes that had twitched nervously at that.

“No, thank you!” Gen laughed as he held a polite palm up in rejection, seemingly unfazed by Senku’s challenge.

“You can’t reject a challenge, Gen.” Chrome joined Senku’s efforts in making Gen suffer with them, prodding and taunting the other man with a big cheesy grin on his face. Despite all their efforts, Gen kept refusing, shaking his head vehemently as Chrome tried to physically push him toward the water as the group had done with Senku. “No- Chrome- I can’t-”

“He can’t do the challenge, Chrome.” Kohaku grabbed Chrome’s shirt and pulled him back and away from Gen. “He… can’t swim.” She reasoned, sharing a private look with Gen before turning her eyes back to Senku and Chrome, as if challenging them to say another word.

Senku had caught the private exchange between the two, but decided not to push any further. As he kicked his shoes off and unlaced the bottom part of his tunic, he wondered if what just happened had anything to do with the curiosity his instincts were directing towards Gen lately.

As he unlaced the final string and allowed his tunic to drop to the ground, he found Gen’s eyes sweeping across his body, seeming surprised to meet his own and quickly fleeing back to studying the fire’s embers. A whisper of scientific intuition told him to hold onto that little data point as he took a deep breath and jumped into the ice cold water.

The water was as harsh as Senku expected it to be, and he found himself on all fours, wheezing, as he arrived back at the muddy shore, no snow to be seen after the salty water melted it away. He knew he had to gather up the strength to put his clothes back on and warm up near the fire if he wanted to avoid getting sick, but he couldn’t help but feel frozen in place, teeth chattering as he shivered uncontrollably.

“I guess you won’t be the most blessed this year.” Gen joked as he walked towards Senku, who had smelled his scent minutes before he had even gotten close. Before Senku’s cold-stricken brain could think of a retort, he found a layer of cloth being wrapped around him.

“Here,” Gen said gently near Senku’s ear as he wiped his skin dry with the cloth. “I’m not a big science man like you, but I know that leaving water on your skin will take away all your body’s heat.” He smiled as Senku glanced up at him with a grimace that was meant to be a smile, unable to think through the cold he was feeling. Taking the cloth from Gen, he finished drying off before quickly slipping back into his animal skin tunic. 

He accepted his shoes from Gen with shaking hands. “Thanks.” He breathed out as he stood up and walked alongside the other man towards the bonfire, his body warming up awfully slowly. “Who ended up winning?”

“Kohaku, of course.” Gen smiled. “Though Magma was a close second.” His eyes fell to where Senku was attempting to rewrap the cloth around his forearms, fingers too unsteady to perform the task well. He tried to remain quiet, but curiosity got the best of him. “Why do you wear those there?”

“Hmm…” Senku hummed as he paused and looked up. “I would tell you, but then I would be revealing my secrets.” He grinned mischievously, laughing as Gen rolled his eyes.

“Senku~! Scientists aren’t supposed to have secrets.” He pouted in an attempt to get Senku to spill, though he already knew the other man wasn’t weak to such emotional appeals. If it wasn’t a logical plea that had a justifiable reason behind it, Senku wasn’t interested in hearing it.

“Well, maybe if you let me know how you get your essential oils, I’ll let you know why I wear these.” Senku grinned, a glimmer of challenge in his eyes. Gen’s irises betrayed his discomfort with the topic for a nanosecond before he schooled his features back to their sly nature.

“Then I guess neither of us will ever really know.” Gen smiled easily and turned back to face the rest of the group, his eyes watching the annoyance on Senku’s face from the side. 

Gen chuckled to himself as he let the younger man fuss with the cloth wrapped around his arms, getting up to get him a warm herbal tea to help him warm up. Despite thoroughly enjoying messing with Senku, he knew that maintaining the man’s optimal health was top priority for their survival and development. Yes, he told himself as he poured the drink into a molded cup, his concern was purely from a survivalist perspective. Any secondary care that he felt flutter in his chest when he saw Senku shivering and shaking was simply a side effect of being so invested in his own success.

He nodded to himself, then carried the drink back with ever-present elegance in his step.

* * *

When Senku retired to his bedroom that night, he was surprised to find that neither Gen nor Chrome hadn’t followed him there. Recently, the three of them had taken up the habit of sharing the room and laying down their sleeping mats next to one another- it allowed them to discuss their plans for the next day until they drifted off to sleep. Sometimes, Gen would be the only one to sleep there with Senku, and sometimes it would only be Chrome. Rarely, however, would it be neither one.

So Senku found himself tossing and turning with frustration. Before the petrification, he had never shared a room with anyone, and had never developed the dependence on others’ presence. Now, though, he found himself stirring at every little scuttle and whistle of wind in the room. Aside from that, though, he felt a strange anticipation just under his skin. Like his body knew something that his brain didn’t. It agitated him to no end, though he eventually bored himself to sleep by reciting the digits of Pi that he could recall from memory.

With a night of sleep as awful as that, he had to hold back cursing as Suika burst into his bedroom from the ladder outside, shouting his voice urgently.

“Senku! You need to get up! Please, it’s an emergency!” She pleaded with him as she tugged on the blanket he slept under.

Shit. Did Tsukasa attack already? Did he predict the attack timing wrong?

“I’m up. What happened?” He asked, sitting up quickly and rubbing the sleep (or lack thereof) out of his eyes, the light streaming from outside too harsh to bear. “Is Tsukasa here? Is everyone in position?” He rushed out from under the blanket, sliding on his shoes with adrenaline flooding his system. The fight. It was finally here.

“No, no, it’s not Tsukasa.” Suika shook her head vehemently, causing him to pause. If it wasn’t Tsukasa, then what was the problem? “It’s Gen. He’s sick. He’s burning up, that’s what the elders said. Is he going to set on fire?” She cried loudly in fear, eyes wide under her watermelon helmet. 

Senku laughed despite himself at that. “No, he’s not going to combust. When they say burning up, they mean it’s a high fever.” He patted her helmet gently. “I’m not sure why he’d be sick, though. He didn’t even swim.” He hummed thoughtfully, pausing to consider the possibilities. Gen usually covered up well. In fact, he exposed less skin than most of them in the village. So if it wasn’t from the cold, did he eat something rotten or poisoned? That was possible. Now that Senku was thinking about it, he realized that Gen’s cheeks had appeared a little flushed last night, though he’d assumed it was from their proximity to the bonfire.

Well, it was better to think of possibilities on the way. He was sure that Gen wouldn’t want to be kept waiting. “Can you show me to where he is right now, Suika?” He asked, smiling down at the kid as she nodded and quickly led him down and outside. As he followed her, walking calmly while her little feet jogged ahead of him, he felt a prickle of worry poke his heart. What if he couldn’t figure it out? What if it’s a sickness from the pre-petrification times, a sickness that he didn’t have the technology for?

He shook his head as they crossed the bridge to the village. Thoughts like that had no place in his psyche. If he could build a cell phone, he could cure Gen.

They approached Ruri’s living space in the village, Gen’s signature scent playing in the air outside a few feet away from entrance. How was that possible? What kind of essential oil was strong enough to linger in the air distances away from its carrier? How intriguing.

Entering the tent, he noted that the scent was especially pronounced that day. If it had been anyone else, he would have thought they were insane to apply perfume when they were sick as hell. As it was, this was perfectly characteristic of Gen’s love for primness.

“Senku, you’re finally here!” Ruri exclaimed, rushing over to where he stood. “Gen is running a very high fever. Ginro and Kinro found him collapsed just outside of village territory and brought him back here. He’s awake right now, if you want to talk to him.” She spoke with a low tone, standing close to him so Gen wouldn’t overhear her. “He’s a little grouchy, too.”

“Grouchy isn’t too surprising if his fever is as high as you’re all saying. Let me see.” He approached Gen on the bed, the other man watching him with puffy eyes and sheets pulled up all the way to his chin. “Hey, you. You’re looking worse for wear.”

“Senku, I’m not sick. You have to believe me and convince them to let me outta here. They’ve kept me in this bed all morning.” Gen pleaded with him, scooching away a little so Senku could settle on the bed. The movement released a wave of his scent, and Senku’s lungs automatically breathed it deeply, as if they had been waiting for just that. Odd. Was he getting behaviorally conditioned to Gen’s scent somehow?

“Let’s see.” Senku smirked, reaching a hand to touch the other man’s forehead. Burning up, as it turned out, was an understatement. He now understood Suika’s panic about Gen spontaneously combusting. “Gen, your fever is out of control.” He said seriously, a concern for the man growing in his chest. “We need to break your fever. You’re not going to like this.”

“No, Senku, I swear I just run hot.” Gen promised. “Please, you have to trust me when I say that I’m not sick.” Senku felt conflicted. On the one hand, reason told him that this fever was bad, _really_ bad, and on the other hand, his instincts were telling him that this wasn’t the usual case of illness that he was thinking of. He couldn’t make up his mind on what was going on, but he knew he had to take the first step in counteracting this strange development.

“Well, even if you’re not, your temperature is not sustainable. Your cells are going to fry if your fever increases. We have to get you out of these sheets.” Senku said, looking towards Ruri and nodding at her to help him remove the sheets. “I think I’ll take him to sit outside in the snow for a little bit, he can sleep in the storeroom after.”

“No- wait!” Gen exclaimed loudly, causing them both to stop and look at him curiously. “Um, Senku, is it okay if Kohaku sat with me and took me to your place instead?” He smiled sweetly.

“Why?” Senku frowned in confusion. “Kohaku’s busy training the fighters.”

“Well, _you’re_ chief. You should be busy prepping all the things for our battle. I know Kohaku would rather her be interrupted than you.” Gen’s sickly sweet smile stayed plastered on his face, and Senku knew he was up to something by his exaggerated antics. Or maybe the fever had finally melted his brain and now it was concocting manipulative plans for no reason other than to mimic past neural memory. He figured it was better to keep Gen’s brain cells working than not, so he agreed and went to inform Kohaku himself, missing Gen’s scent with each breath of cold air he inhaled.

* * *

It was arranged for Gen to sleep in Senku’s bedroom, though he had made Kohaku insist that Senku, and only Senku, could _not_ enter or sleep there under any circumstances. Which was why Senku found himself sleeping outside near a small fire, grumbling with each gust of cold wind. At least Chrome had slept there with him in a show of solidarity.

Still, Senku couldn’t shut his mind off. He kept his eyes trained on the window of his bedroom, and when the tarp that covered it swung with the wind he was able to catch a glimpse of Gen. Gen, who seemed to be sitting on the ground of his bedroom, hunched over in _pain_.

Senku sat up in alarm, turning to inform Chrome so he could go check on the man, only to find Chrome fast asleep. He didn’t have time for Gen’s mindgames and stupid rules banning Senku from the room. If nobody could help Gen he had to go in there himself.

He rushed to where Gen was, his feet carrying him through the snow and up towards the bedroom. He staggered inside the moment he pushed the door open, Gen’s scent greeting him, dangerously dizzying. It was as if he had stepped into an ocean of Gen’s scent. As if the man had bathed in a tub of concentrated lavender and oranges, sprinkled pine and black pepper all over the room, and then doused himself and everything around him with something sickly sweet like vanilla icing.

“Gen.” He managed to force out between clenched teeth as he steadied himself against the wall. He had nearly fallen to his knees, and when he searched in his mind for words, he found that he couldn’t make out his own thoughts. He inhaled once again, and felt another wave hit him. The world felt like it was spinning, and the two of them were somehow at the epicenter of its storm.

“Senku!” Gen gasped, appearing incredibly small on the floor of his bedroom, his robe and pants long discarded with only a tunic over his body. “Why are you here? You need to leave.” He made as though he was going to stand up, but crumpled back down weakly, knees giving way with no resistance. “Please, you have to go.” He sounded desperate, and Senku rushed over to him, a fierce need to cocoon the man overwhelming him. A part of him was afraid, terrified even, of what he was feeling. That fear only grew as he touched Gen’s skin, an electricity shooting through him in a way that he had never known before except in the shitty romance novels his aunts would read.

“Gen.” He ground out between his teeth, a growl that sounded foreign to his own ears. His eyes caught Gen’s and he placed a hand on the other man’s cheek, cupping his jaw as gently as he could with the nerves running up and down his arms. “You have to tell me what’s happening. I can help.”

“Senku, I can’t.” Gen whispered, the tears brimming in his eyes punching Senku’s heart. “Senku, you have to go. I can’t- we can’t-” He cried out suddenly, hunching over in pain and clutching his stomach. Under his legs, a pool of some sort of liquid was beginning to grow. A pool of liquid that smelled like vanilla icing…

...Senku had a feeling he was getting closer to the truth he had been trying to understand about Gen all along. And yet it still evaded him.

“Gen,” He started, rubbing the other man’s back gently. “I can make it better.” He said simply, unsure where the words were coming from.

“What?” Gen raised his head, the longer strands of his hair scattered every which way. “You know about this?”

Senku shook his head. “I don’t know what this is. But I know that I’m the only one who can fix it.” He brushed Gen’s hair back softly, the heat flooding his system a reassurance that only reinforced his resolve. “I’m right, aren’t I?”

Gen hesitated, appearing small with Senku’s arms bracketing him. “I can’t ask you to do this. Soon...soon I’m not going to be able to reason with you, Senku. I won’t be able to listen to reason either. This… it can only be fixed by you, but once it starts you won’t be able to stop. Do you understand?” 

Senku nodded slowly, staying silent. 

“Do you know what I’m talking about?” Gen asked, exasperated as Senku shook his head. “I…” Gen’s face heated up, his cheeks growing pink as he looked down at where his hands rested on his own lap, wrapped around each other so tight that the tips of his knuckles turned white. “You have to fuck me, Senku.” He said, looking back up as Senku drew in a sharp breath. “See? I knew you wouldn’t want- to...” He faltered as he recognized the smirk that appeared on Senku’s face. It was his turn to take a shallow breath as Senku drew closer, their faces mere millimeters apart.

“I had a feeling it was something like that.” Senku chuckled, his hands going to take Gen’s in between them, his thumb loosening them with soothing circles before he trailed his fingers up Gen’s arms, a shudder making its way through the older man’s body. “I…” Senku began as he pulled Gen towards the sleeping mat that had been left there for Gen to rest in. “want you, Gen.” He let his arms hold Gen upright as the two of them sat on the mat, neither one daring to take a full breath lest it break the moment, a universe where only the two of them existed. “Will you have me?” Senku finished, swallowing in a nervousness that Gen had never seen from the man before.

The air stood still as Gen studied the other man’s face, thinking that he would have teased Senku for his flushed cheeks on any other occasion, but he wasn’t that cruel. He could feel Senku’s cock brush against his thigh, slick rushing out of him at the thought of it, and he quickly nodded, voicing a hoarse yes.

The younger man didn’t need to be told twice as he let Gen lay back on the mat, taking his legs and bracketing them around himself. He leaned forward, lips hovering just above reach from Gen’s as his fingers worked the tunic off of the man under him. 

Naked, Gen blushed, going to draw his legs back to his body but getting stopped by Senku’s commanding hands. He relaxed his legs in Senku’s hold, breathing shallow breaths as he watched Senku’s eyes, usually calculating, now drunk with lust, rake over his body. Senku was watching him like he watched his most prized inventions, he realized, and another rush of slick spilled out of him. “Senku, you’re staring.” He whispered, afraid to raise his voice any louder and shake Senku out of his trance.

“I’ve never seen anything like it…” Senku whispered back, his hands roaming across Gen’s body with a delicacy so dangerously close to love that Gen’s heart seized up, his lips traveling down to kiss the inside of Gen’s thigh. “Your body, it’s beautiful.”

Gen allowed the tears in his eyes to spill, biting his lip to hold a sob back. His head was swimming with want, and he cried out as Senku’s hand gripped his cock, his lips brushing against his dripping cunt. “Fuck, Senku.” He gasped, the shock of contact causing him to involuntarily jolt away from the sensation, though Senku’s other hand remained firm on his left thigh. “Please.” He whined, blushing at the sound of his own desperation.

Senku growled in response, the sound of Gen’s whines shooting straight down to his own throbbing cock. His lips encircled Gen’s small cock, sucking slowly before shifting to a punishing pace. The moans that escaped Gen’s lips were intoxicating to his ears, and a few minutes later he released Gen’s cock with a loud ‘pop’.

“No- don’t stop baby-” Gen pleaded, face glimmering with sweat in the moonlight.

“Shh, I’m here, I’ll take care of you.” Senku promised before licking Senku’s cunt lightly, taste buds exploding with sensation at the taste of the other man’s slick. He growled, pushing his tongue in to eat his cunt greedily, drinking down Gen’s sweet nectar as Gen’s shouts echoed around the walls of the hut. 

Senku’s own cock was oozing precum under his tunic, and he broke off from Gen’s wet cunt to hurriedly remove his clothing. “Fuck, you’re driving me crazy, Gen.” He breathed heavily, each breath drawing him closer to addiction to the sweet smell that surrounded him. He felt blinded, by Gen’s scent, by his soft skin, his sweet cunt. His thoughts melted away, replaced by a primal urgency to fuck the other man, to ruin him for anyone else should they come after him.

Throwing his tunic across the room, he leaned back down, hand gripping the back of Gen’s neck as he kissed him frantically, heart exploding as Gen kissed him back just as fiercely. He felt Gen’s hand wrap around his cock and groaned as his ministrations nearly brought on his climax. He broke their kiss, both men panting with want. “What do you need, my love?” He asked Gen gruffly, the adoring title rolling off of his tongue before he could think to stop it- or think at all.

“You.” Gen begged, his hands moving to grip Senku’s hips desperately. “I need you inside me, Senku.” He pleaded, pupils blown out wide with lust. Senku groaned, gripping the base of his own cock to stop himself from climaxing just at Gen’s words.

“Fuck yeah.” Senku hissed as he lined his cock up with Gen’s tight hole, his head pushing against his soft, plump pussy. He carefully pressed until his cock was sliding in, a groan escaping his lips at the tightness wrapping around him. If any thought had been left in his brain, it escaped as he pulled his cock back and pushed it back in. Gen’s cries fueled his pace until he was mercilessly thrusting deeper into the man, throwing Gen’s legs over his shoulders and gripping his hips forcefully. “You like that?” He growled out, folding Gen easily as he leaned over him.

“Yes, yes, Senku,” Gen babbled, eyes rolling back. “Love it so much, love your cock.”

Senku growled, a deep rumble in his chest as he pounded into the other man, dizzy with lust and affection and possession. Somehow, the pressure in Gen’s cunt was growing around him, as if his cock was expanding with something. He let Gen’s legs fall on either side of him as Gen captured his lips in a searing kiss, a feeling of anticipation pooling at the bottom of Senku’s abdomen. He trailed his lips down to Gen’s neck, kissing and biting hungrily. He felt his instincts drawing him somewhere, somewhere, and then his nostrils were flaring as the most heavenly scent flooded them. His vision whited-out as the knot that had formed at the base of his cock blew wide inside of Gen, growling as he bit down on Gen’s shoulder.

“Fuck, Senku!” Gen moaned as Senku’s fat knot stretched him wide, cunt clenching down on it greedily as thick spurts of cum filled his insides. He moaned as Senku’s hand went to his cock, enveloping it as he rubbed it ruthlessly. Senku rocked his knot inside of him, teasing his G-spot with it until Gen reached his own orgasm, crying out as his cum painted Senku’s hand and both of their stomachs.

The sound of their breathing was deafening as they stared at one another in silence, eyes wide in awe at the sheer pleasure, locked to one another by Senku’s knot. Senku released Gen’s cock, bringing his hand to his lips and licking his fingers clean.

“Fuck.” Gen’s mouth dried as he watched, his cunt twitching in arousal and sending a wave of overstimulation from where Senku’s knot brushed his walls. “At this point you’re torturing me.” He hid behind an arm, letting one eye peek out at the younger man still lapping up his hand. “Is it really that good?” He asked as he and Senku shifted so they were laying on their sides, facing each other with their bodies locked.

“You don’t even know.” Senku said seriously, leaning close and kissing his lips to share the taste with him in a move that only aroused Gen more. Making out with Senku only served to build his heat back up again, and he grinded against Senku’s deflating knot, biting his lower lip to hold in a whine. He could feel his heat still raging in his body, skin itchy and head dizzy with fever. He knew he would be needing much more of Senku’s ‘help’ to get through it, and, well, he _wanted_ much more of Senku now that he’d had a taste.

“Well,” He glanced at the window, making out the glow of moonlight from in between the tarps, before turning back to Senku. “The moon is still out.” He smirked, gasping as Senku slid his cock out of him suddenly. Now unobstructed, he could feel Senku’s cum trickle down and out of his cunt.

“It is.” Senku agreed, watching him calculatingly as he sat up. Gen’s smirk never left his face as he pushed Senku onto his back and straddled his waist.

“Care for another round?” He asked innocently as he felt Senku’s cock harden in interest beneath him. He knew the answer before Senku even uttered it, crying out in ecstasy when Senku buried his cock deep inside him.


	2. Chapter 2

**Notes for the Chapter:**

> Possible TW: Discussion of possible Mpreg and general angst around it.
> 
> I quickly wanted to say thank you for all the love shown for this fic! I'm blown away at 74 kudos from just one chapter, I never would have expected it! Appreciate you all, and I hope you like this update! <3

“Yes, Senku-  _ God _ !” Gen grip on Senku’s hair was tight as the younger man’s tongue fucked him in earnest. He grinded against the man’s face, feeling heat building across his body as he neared his climax. “Fuck, I’m coming!” He warned. Dark spots filled his vision as Senku maintained his steady rhythm, pushing him over the edge. Spurts of cum landed on Gen’s own abdomen as his cunt released a stream of sticky slick into Senku’s mouth, coating his reddened lips with shiny sweetness. Senku’s tongue exited his hole, lapping up at his pussy’s soaked lips before coming to lay down next to him with a satisfied sigh.

Gen breathed raggedly as he watched the other man, studying his face shamelessly while Senku had his eyes closed in serenity. Or deep thought. 

Although this entire arrangement had been done to help Gen through his...whatever that was, he couldn’t help but notice how much it had benefited the other man too. The tension that had once been coiled tight around Senku’s slim muscles had finally released its hold, allowing the younger man to breathe. He realized that he might be seeing Senku truly relaxed for the first time since he’d met him in this stone world, and felt a glimmer of pride at the thought that it was  _ his _ doing,  _ his _ body that had facilitated that.

“So, are you going to tell me where you learned that?” Gen teased as he flipped over to lay on his stomach, head resting on his hands as he watched the other man’s expression. He loved to do that, to sit and watch the tell-tale shifts in Senku’s face at his words. It had been what drew him to the man in the first place, the sheer honesty that gladly revealed itself with Senku’s every word, every move. He was no oversharing idiot, of course, he simply had nothing to hide. A man so confident with the hill he stands on, a hill of accumulated human knowledge and wisdom, that he was willing to sacrifice himself for it.

When faced with a man as passionate as that, how could Gen ever expect anything but the butterflies that tickled his stomach?

Still, in all of the nights and days he’d spent dreaming of a world where he and Senku could be  _ anything _ , he never thought this stone world would be the one to make it happen. Those nights when he’d share Senku’s room and Chrome would fail to show up, leaving the two of them to chat away until sleep got the better of them, they were the dearest memories to his heart for the longest time. Now, he had new memories, ones that sent his heart hammering away, warming his ears until they were pink with bashfulness.

“I don’t kiss and tell, mentalist.” Senku grinned, pulling Gen from his reverie and physically pulling him so his head rested on his chest. It was a strange habit that he’d developed during their coupling, though Gen wasn’t going to ruin it for himself. Of course he’d known about the tenderness Senku carried in him, he brought it everywhere he went. It was why people flocked to him so easily. Senku might want to act like a cocky, goal-oriented man with no time for sentimentalities, but Gen had seen firsthand the lengths he’d go just to put a smile on someone’s face. After all, didn’t he do just that for Gen despite fully knowing that he would have returned to stand by his side, cola or no cola?

Gen chuckled softly to himself at his musings, not bothering to share them and Senku not bothering to ask.

“Oh? So gentlemanly, even after civilization has fallen?” Gen glanced up, smirking. “I suppose I should be glad that you’re such a good secret keeper, since we just created quite the secret.”

“Civilization hasn’t fallen, not with the two of us plotting its comeback.” Senku smirked, hand pushing Gen’s longer strands behind his ear tenderly. “And I doubt this will be the best kept secret, I think people might have noticed our extended absence by now.”

“Hm, easy. We’ll just say we’ve been so hard at work planning our next grand project that we lost track of time.”

“And this grand project is so exciting that the noises coming from this storeroom are perfectly inconspicuous?” Senku retorted, smirking cockily as Gen’s face turned a bright pink.

“Might have forgotten about that part.” Gen mumbled, pushing on Senku’s chest with his fist lightly as the man cackled at him. He tucked his face in the crook of Senku’s neck to hide his shame, finding refuge in the other man’s scent, roasted almonds and fresh-brewed coffee and  _ warmth _ . The two fell into a peaceful silence, a calm washing over both of them as easily as breathing.

“You know, this whole time I thought you were using essential oils.” Senku mulled as his hand brushed up and down Gen’s back softly, his touch delicate against Gen’s smooth skin. He was idly connecting the petrification scars there, the ones that Gen kept hidden beneath layers of clothing. He shivered at the tickle of Senku’s calloused fingertips, rough with the assembling and mixing he did day and night for their shared vision of a revived world.

“Yeah, that was quite entertaining.” Gen chuckled, his left index traced circles on Senku’s chest, feeling the hitch in Senku’s breathing as his cool fingertips met soft, warm skin. “I never thought I would see the great Senku Ishigimi stumped by something so obvious.”

“I suppose a real scientist would laugh at me too, huh?” Senku’s lip quirked up, his eyes watching something beyond the bamboo ceiling above them, perhaps looking at the ideas still forming in his head. “Still, this  _ nature _ was only observable in some non-human animals, pre-petrification.” He fell into a thoughtful silence and Gen let him, almost hearing the gears turning in Senku’s head from where he lay.

“Were you intersex before the petrification?” Senku asked simply, his tone softening the directness of his question.

“No.” Gen’s voice was soft to his own ears, a sound adrift in conflicted emotion. He did not hate this new biology, but rather, he had seen for himself how it had changed the status of some people in Tsukasa’s camp. Once modern timers discovered people like him, they were quick to establish some unfair dynamics, an insult to the advances in gender and queer theory that Gen and many others had spent years studying in college. Did all of those things mean nothing to them? Did the temptation of pure animal instincts with no remorse beat down their morals that easily? And what if the villagers here came to learn what Senku now knew, would it change his value among them? Worse yet, would it change the respect and dignity between him and Senku? What happened to people like him in a world with no rules? These questions had kept him up for many nights in Tsukasa’s empire, and now he felt himself drowning in their implications all over again.

“Hey, mentalist.” Senku drew him out of his spiral. “Your thoughts are loud.” He pulled back to look at Gen better from where he lay. “The long period of petrification must have altered our biology somehow. The knot that forms on my dick around you,” His voice grew low at that, repressing lust that the finger he trailed languidly across Gen’s stretched stomach betrayed. Gen held his breath, ears warming, sensitive to touch where some of Senku’s seed still filled him. “It’s confirmation that being petrified must have changed us somehow. Mine only appears around you, and yours… well,  _ you _ must have had some kind of biological advantage over me that made you fit for developing the biology that you now have.” Senku paused, making new connections in his head that Gen could not see. “If I’m right about the connection to the biology of wolves, that makes you…” Senku trailed off, his scent spiking with the excitement of a new thinking problem, a scent Gen was all too familiar with, having witnessed the man’s many instances of sudden scientific insight.

“Makes me what, Senku?” He asked with fondness in his tone, reminding Senku of the other person in the room that he needed to keep in the loop. He propped himself up on one elbow, feeling a surge of nervous excitement shoot down his back that brought the acidic, citrusy undertones of his scent to the fore.

“It makes you an omega.” Senku sat up, his hand cupping his chin thoughtfully as a million realizations and considerations probably dawned on him, ones that Gen could hardly catch up with.

“What’s an omega? And why is that important?” He asked curiously, noting some of the tension returning to Senku’s body, his scent turning into a darker, richer scent of dark roast coffee. Gen’s nerves automatically stirred at that, but he refrained from letting his anxiety run wild. Whatever Senku was realizing, whatever was bringing that edge of anxiety to him, he knew that the man would be sharing it with him in due time. After all, who else would he share it with if not his confidant?

“You never learnt this, in school?” Senku asked, humming as Gen shook his head. “I suppose I didn’t learn it there, either. Maybe from one of the books I read.” He shifted so he was sitting on his heels, facing Gen with a patiently gentle gaze. “In the animal kingdom, the omega is often at the bottom of a pack’s hierarchy. They’re usually subservient to the rest of the pack, even if they’re the strongest objectively.” Gen’s heart sank at his words, thinking back to the treatment of the men and women like him in Tsukasa’s group. He clenched his teeth behind closed lips, hands forming into tight fists. Of course, if his status is biologically driven, then Senku wouldn’t reject its logic. 

“However,” Senku raised an index finger, his other hand landing on Gen’s clenched fist as if aware of his thought process. “As humans, we’re gifted with the thinking brain. For us, an omega might simply be a unique member of a group, granted the ability to pair with an alpha.”

“What’s unique about that?” Gen’s face was flat, betraying his irritation. He didn’t want to say the rest, that he didn't see what privilege there was in just being the sex toy of some other member, some  _ alpha _ . Even if that alpha was Senku.

“Well,” Senku began, “I’m assuming, and this is just a theory, but… it might mean that you are the only one capable of carrying and delivering an alpha’s child.” He grimaced, his cheeks red at the implications. 

“A child?” Gen frowned. “Surely not?” A nervous laugh left his lips, eyes betraying his desperate need for Senku to say he had only been joking.

“Think about it, Gen.” Senku chewed on his lower lip, anxious with the thoughts swimming in his head, another tell he’d never show to most except here alone with Gen. “Why else would your biology be what it is right now? Why would you go through heat, like what happens in the animal kingdom during periods of mating? And why was I unable to resist you, your scent, during that time?” His tone was delicate, sensing the paper thin calm that Gen was holding onto. Taking in Senku’s face, Gen hated finding honesty still in it. This was no joke.

Gen blinked once. Twice. With all the things he’d prepared himself mentally for in life, this was something he’d never thought he’d have to worry about. He found himself looking down at his pelvis, feeling as foreign from it as the day Tsukasa had revived him. He looked back up at Senku and felt far from him, carried far into an unknown ocean by the lazy ebb and flow that people so often disregarded as harmless. 

An old, forgotten memory returned to him, of holding his parents’ hands in a dry desert far from Japan, most likely on one of their family holidays. His father’s words rushed back, reminding him to stay on the flat patches no matter what, especially when a giddy excitement came over him and urged him to scale the giant sand dunes surrounding them. He asked why, a stubborn, curious child, and found out what happened to those who succumbed to the sun’s powerful influence; on top of the world one second, and delirious, trapped, with no hope of navigating back down the next.

Sitting opposite Senku, with the difficult truth sitting between them, he felt awfully similar to those who’d succumbed to the alluring dunes, shining with the color of gold. The heat he’d shared with Senku was just like that desert sun, a tantalizing siren that fooled those who jumped without thinking.

His stomach turned nauseatingly at the thought of carrying a child, and he had to swallow down the unease that crawled up his throat.

“Fuck.” Gen whispered, hardly able to get the word out. His eyes fell on Senku’s hands, noting the shake in them that usually betrayed the anxiety he kept tightly locked away from others’ eyes. At least, Gen thought gloomily, the two of them were stuck on the same menacing sand dune together. 

The sickly feeling in his gut made his vision swim and he pulled his knees to his chest. The harshness of daylight felt too much for his sensitive eyes so he screwed them shut, hiding his face in his knees in an attempt to manage his state. The air around them was cold, yet he found his body sweating with dread.

“We were fools.” He mumbled, suddenly wishing either one of them had weighed the situation more thoughtfully instead of succumbing to their wants. He had wanted and still wanted Senku more than anything, and had felt that same desire mirrored in the other man’s soft caresses. 

How could they have known? He’d known that an alpha was the answer for his fever because of the heats he’d witnessed in others like him in Tsukasa’s group, but he hadn’t stuck around long enough to learn of the consequences.

That night that Senku barged into the storeroom, eager to comfort, to protect, to  _ please _ , Gen’s heart sang louder than it ever had before. That same heart now twisted in regret, not for what they had done, no- he knew he would always choose Senku, in every world. It was regret for not having  _ known _ so they could at least have the power to choose this possible outcome to a mutual affection they'd always held for one another.

Fear’s icy tentacles painted the chambers of his heart as he wondered if Senku regretted ever touching him. If he did, Gen knew the knowledge of hurting Senku like that would kill him.

The should’ves and could’ves taunted him in his head and he gritted his teeth against their punishing claws. They wanted so desperately to escape his lips, to be shared with Senku so he too felt their sting, but what good did such ruminations do? They were only a vehicle for torture, a punishment for them both. Gen knew that much even in his current state. 

Biting his lip, he tightened his embrace on himself and shut the world away.

“Gen...” Senku’s hand landed on his arm gently, and Gen hated himself for the small comfort it brought to his heart. He wanted to hate Senku for the curse nature had thrust upon the two of them, but a feeling told him that even without their biologies, their hearts would always have found one another anyway.

Tsukasa, unbeknownst to even himself, had revived the best trump card he could ever ask for in the battle against Senku. That day he revived Gen, it had spelled the dawn of a new, dangerous vulnerability for the scientist. Even if Gen and Senku were to fix that vulnerability before it became known to others, it would remain a painful memory, a dark and somber knowledge, locked away in the depths of their minds.

One a logician and another a strategist, there was no hope for them to choose anything but the most assured victory. But still… Gen knew the sentimental nature he shared with the man sitting before him, and that triggered a pang of guilt in his chest at the fate he had already begun to accept for the life likely to grow inside of him.

“What are we going to do, Senku?” Gen’s lips shook in defiance of a sob that he didn’t know was inside of him. He wanted to look at Senku, but he was afraid of what he could find. Regret or revulsion, disdain or dominion… or worse, a man broken by  _ him _ . By  _ his _ body.  _ His _ stupidity.

Why hadn’t he bothered to find out back then, what happened to those other omegas?

“It’s not my decision.” Senku took Gen’s hand in his own, rough palms against Gen’s smooth ones. “I could never make that decision for you.” He squeezed, his other hand lifting Gen’s chin so red eyes met blue so overcast with the angst in Gen’s heart that they appeared grey. “But I will be  _ here _ . I said as much before, didn’t I?” He tried for his signature smile on Gen of all people, as if he didn’t know the man enough to see right through it.

A choked sob left Gen’s lips at Senku’s words, guilt eating away at his heart. He felt guilty for himself, for Senku, for this possible life that he knew they couldn’t afford. Guilt beat down on him like a hurricane and he worried that it would drown them both in his tears.

“That was different.” Gen said brokenly and looked down, face obscured by long locks of tousled hair, tears running freely down his face. He thought back to Senku’s whispered promises and praises, fueled by the passion of their shared heat. In the harsh light of day, they felt to Gen like words only fools would say.

Between them, the air smelled acidic, carrying the unspoken pain in their scents. Gen wanted to laugh at the memory of his past self, the one who had daydreamed of something more with Senku, and found that it only made him cry harder.

**Notes for the Chapter:**

> As usual, feedback is super appreciated, but I especially love to hear from you in the comments! <3
> 
> Here are some more headcanons revealed in this chapter, if you're curious:
> 
> \- Only LONG petrification leads to the development of an alpha or omega assignment. That's why if these characters are hypothetically petrified again later, they wouldn't switch assignments unless they were petrified for as long as 3000+ years again. It's also why the villagers don't have this biology that Senku and Gen are experiencing, cause they were never petrified so they descend from humans like us!
> 
> \- Alphas only form a knot if they're engaged in something sexual with an omega, that's why Senku didn't realize he'd changed too until seeing Gen in heat.
> 
> \- Omegas are still able to remember heat sex and everything during and after their heat, they just feel either extremely tired or extremely horny during and that's why they need an alpha to take the edge off or to take care of them. I just don't feel comfortable making their heat fuzzy because consent cannot truly be given in that case.
> 
> I can't think of more, but please feel free to drop questions in the comments or via twitter!
> 
> Thanks for reading, see you in the next one :)

**Author's Note:**

> All feedback is super appreciated, but I love to hear from you in the comments! <3


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